Inductive position sensor
A position sensor is for determining the position of a conductive target using a transmit coil and a plurality of receive coils. The receive coils may each include two strands and a strand may be obtained from a conversion of a substantially sinusoidal primitive function. The position sensor may realize a reduction of harmonics in signals from the receive coils.
1 . A linear position sensor for determining a linear position of a conductive target, the position sensor comprising:
at least one transmit coil;
a first, second and third receive coil enclosed by the transmit coil, wherein each receive coil has a predefined electrical period which is the same for each receive coil and wherein each receive coil comprises a first conductive strand and a second conductive strand, wherein the first strand is obtained from a primitive function which is scaled given the electrical period, and wherein the primitive function of the second strand is the primitive function of the first strand shifted over 180°, and wherein both strands are electrically connected so that a continuous coil is formed with two open ends, and wherein the primitive function of a strand of the second receive coil is the primitive function of a corresponding strand of the first receive coil shifted over 120°, and wherein the primitive function of a strand of the third receive coil is the primitive function of the corresponding strand of the first receive coil shifted over 240°;
the conductive target which overlaps the receive coils; and
an integrated circuit which is configured for exciting the transmit coil, thus inducing signals on the receive coils, and for reading the signals from the receive coils or a combination of the signals, and for processing these signals, wherein the position sensor is configured for removing a common mode signal from these signals.
2 . The linear position sensor according to claim 1 , wherein the conductive target has flanges arranged in a periodic arrangement and wherein the flanges are identical.
3 . The linear position sensor according to claim 1 , wherein the first strand and the second strand are provided on a printed circuit board.
4 . The linear position sensor according to claim 3 , wherein the first strand and/or the second strand alternate between a first and second side of the printed circuit board for enabling crossings between both strands.
5 . The linear position sensor according to claim 1 , wherein processing the signals comprises offset compensation of the signals.
6 . The linear position sensor according to claim 1 , wherein processing the signals comprises extracting a position of the conductive target from the obtained signals.
7 . Use of a linear position sensor according to claim 1 , wherein:
the transmit coil is excited using an excitation signal;
signals from the first, second, and third receive coils are read; and
the obtained signals are processed for obtaining the position of the conductive target, wherein processing at least comprises removing a common mode component of the received signals.
8 . A method of forming a linear position sensor, the method comprising:
defining a substantially sinusoidal primitive function;
scaling the primitive function given a predefined electrical period;
obtaining a second strand from the primitive function shifted over 180°;
obtaining a second receive coil, wherein the primitive function of a strand of the second receive coil is the primitive function of a corresponding strand of a first receive coil shifted over 120°;
obtaining a third receive coil, wherein the primitive function of a strand of the third receive coil is the primitive function of the corresponding strand of the first receive coil shifted over 240°;
providing a conductive target which overlaps the receive coils; and
providing an integrated circuit which is configured for exciting a transmit coil, for reading signals from the receive coils, and for processing these signals, wherein processing the signals comprises removing a common mode signal from these signals.